Described below are a method and system for power control for radio communication within a device which can fly.
Spatial areas are known in which it is undesirable for private subscribers to use radio communication terminals or mobile radio communication terminals, or in which the use of radio communication terminals must be regulated.
By way of example, these spatial areas include sensitive areas in hospitals in which it would be possible for radio wave propagation and selected transmission powers when carrying out radio communication to influence equipment functions which are important to life.
This likewise includes aircraft interiors, in which it would be possible for radio communication taking place onboard to have a disturbing influence on the navigation electronics.
By way of example, aircraft are subject to specific requirements relating to the transmission powers of radio communication terminals that are used in the aircraft interior, in order to produce a connection with a central point onboard the aircraft itself. The central point then produces a connection between the radio communication terminal of a subscriber and the outside world via the aircraft radio system.
The aircraft central point may, for example, be in the form of a base station of a radio communication system, in order to allow the subscriber to use his own, private or business-use radio communication terminal in the aircraft.
Since an aircraft base station in this case uses standardized radio transmission resources and radio transmission methods, interference from terrestrial radio communication systems during overflight must be avoided. This interference is measurable in particular at altitudes below 3000 meters.
A further problem results from the fact that a radio communication terminal can set up a radio link to a terrestrial radio network at an altitude of less than 3000 meters, for example, without having to use the base station or central point onboard the aircraft itself. In this case the radio communication terminal will transmit at a very high or at the maximum transmission power level in order to cover the distance to the terrestrial base station, thus possibly resulting in interference with aircraft equipment in particular during take-off or landing.
US 2002/0019229 A1 discloses a base station and all the mobile stations which are connected to the base station in the aircraft being switched off during a landing approach and during take-off. The transmission power is therefore reduced to zero. The landing approach and take-off are detected by means of the remaining flight time, the low altitude, extension of the landing flaps or ground contact of the wheels.
US 2001/0052850 A1 discloses a radio link with a transmitter in order to locate baggage. The transmitter can be switched off during landing and take-off processes. A landing or take-off process is determined by the air pressure in the cargo bay of the aircraft, vibration or acceleration of the aircraft.
WO 2006/075126 A1 discloses a base station simulator which first of all sends a signal to the radio communication terminal in order to set up a link to the base station simulator. In a second step, the base station simulator sends a signal which renders the radio communication terminal inactive.
US 2004/0142658 A1 discloses a transparent system which sends the system identifications of the terrestrial radio systems to the radio communication terminals and therefore either switches them to an inactive state or to a state with a low transmission power.
WO 2007/022418 A2 discloses a method for switching the communication of the base station in the aircraft to the radio communication terminals on or off.
In order to avoid problems such as these, the operation of a radio communication terminal in the interior of an aircraft is envisaged only above a minimum altitude.
In addition, it is necessary to limit the transmission power of the radio communication terminals located in the aircraft interior and of the base station onboard the aircraft itself, in order on the one hand to allow radio links between the radio communication terminals in the aircraft interior and a central point or base station which is provided for this purpose onboard the aircraft itself, and in order on the other hand to prevent or to minimize interference from terrestrial radio communication networks.
On the other hand, it is advantageous to increase the transmission powers of the radio communication terminals and the aircraft base station in the aircraft interior, in order to ensure more robust voice or data transmission, or to increase the transmission rate for data services.